Component comprising a large number of light-emitting-diode chips

ABSTRACT

A device ( 1 ) with a number of light emitting diode chips ( 5 ) in a reflector ( 3 ) is formed in such a way that the direct line of sight between the light emitting diode chips ( 5 ) is interrupted by a partition ( 11 ). This improves the efficiency of the device ( 1 ) substantially.

[0001] The invention relates to an optoelectronic device as generically defined by the preamble to claim 1.

[0002] These types of devices are widely known. Since light emitting diode chips can emit light in various colors, the devices can be used to emit multicolored light. Furthermore, since the light emitting diodes are arranged together in the same reflector, the device remains relatively small despite the multicolored nature of the light emitted.

[0003] However, the light yield of the known devices remains below the total light yields of the individual light emitting diode chips.

[0004] On the basis of this prior art as the point of departure, it is the object of the invention to disclose a device with an improved light yield.

[0005] This object is attained according to the invention with a device having the characteristics of claim 1.

[0006] Since the direct line of sight between the light emitting diode chips in the device according to the invention is interrupted by baffles, only a tiny fraction of the radiation emitted by a light emitting diode chip is absorbed by the other light emitting diode chips. By taking these measures, a major source of occurring losses is eliminated. The light yield of the device according to the invention is therefore essentially the same as the total of the light yields of the individual light emitting diode chips.

[0007] Further advantageous features of the invention are the subject of the dependent claims.

[0008] Below, exemplary embodiments of the invention are explained in detail in conjunction with the accompanying drawing. Shown are:

[0009]FIG. 1, a top view of a device that can be equipped with a number of light emitting diode chips;

[0010]FIG. 2, a cross-sectional view taken along the line II-II in FIG. 1; and

[0011]FIG. 3, a cross-sectional view through a modified exemplary embodiment of the device.

[0012]FIG. 1 shows a top view of a device 1, which is described in further detail below in conjunction with FIGS. 1 and 2. The device 1 has a housing 2 in which a cavity 3 is made. The cavity 3, with its sloped side walls 4, serves as a reflector for the light emitting diode chips 5 which are arranged in the cavity 3. The light emitting diode chips 5 are arranged on a leadframe 6, whose connection elements 7 protrude laterally out of the housing 2. Some portions of the leadframe 6 are located beneath cover layers 8, which serve to fix the leadframe 6. The leadframe 6 is furthermore subdivided into individual mounting areas for the light emitting diode chips 5 and bond pads 10 for the bond wires used for bonding the light emitting diode chips 5. The bond wires used for connecting the light emitting diode chips 5 are not shown in FIGS. 1 and 2.

[0013] The light emitting diode chips 5 are arranged in the housing 2 typically with an interval spacing of 0.8 mm, measured from the center of each light emitting diode chip 5, respectively. Between the mounting areas 9 for the light emitting diode chips 5 is a gap approximately 0.2 mm wide. In the exemplary embodiment shown in FIGS. 1 and 2, the gap in the leadframe 6 between the mounting areas 9 is occupied by the partition 11, whose walls have a wedge-shaped cross section. The direct-sight contact between the light emitting diode chips 5 is interrupted by the partition 11. The radiation originating from one of the light emitting diode chips 5 can therefore not be absorbed directly by one of the other light emitting diode chips 5. For this reason, the light yield of the device 1 is approximately equal to the sum of the light yields of the individual light emitting diode chips 5.

[0014] Because of the wedge-shaped cross section of the partition 11, it is assured that the light striking the partition 11 will be reflected outward. The height of the partition 11 should advantageously be up to 25% and preferably up to 10% above the height of the light emitting diode chips 5. The height is measured in each case from the bottom of the cavity 3 upward. If the height of the partition 11 is lower than the height of the light emitting diode chips 5, the line of sight between the light emitting diode chips 5 will not be completely interrupted. Conversely, if the height of the partition 11 is too great, then the partition takes up too much space, because of its wedge-shaped walls. Accordingly, it is the radiation characteristic of each light emitting diode chip 5, respectively, that is definitive for the height of the partition 11. If the light emitting diode chips 5 primarily radiate downward, then the height of the partition 11 can also be less than the height of the light emitting diode chips 5.

[0015] For producing the device 1, first the leadframe 6 is injection-molded with a thermoplastic or thermosetting plastic, and then the light emitting diode chips 5 are set down on the mounting areas 9 and bonded. Next, the cavity 3 is filled with a resin that is transparent to the radiation of the light emitting diode chips 5.

[0016] It should be noted that the same method can be employed if the leadframe 6 is replaced by a complete printed circuit board. In that case, in the region of the light emitting diode chips 5, the printed circuit board is provided with a housing 2 that is injection-molded onto the printed circuit board.

[0017]FIG. 3 shows a cross-sectional view through a modified exemplary embodiment of the device 1. In this exemplary embodiment, the housing 2 is first formed and then the requisite conductor tracks 12 are made on the surface of the housing 2. For that purpose, what is known as the CIMID technique can be employed. According to this technique, a thin metal film is first deposited in an aqueous solution on the surface of the housing 2, and it is then patterned using a laser. The thus-structured metal film is then thickened by electroplating. Using this method has the advantage that the partition 11 can likewise be coated with a reflective metal film. This further improves the efficiency of the device 1. 

1. An optoelectronic device, having a plurality of light emitting diode chips (5), which are arranged adjacent to one another in a common reflector (3), characterized in that between any two light emitting diode chips (5), a partition (11) is arranged.
 2. The optoelectronic device of claim 1, characterized in that the reflector (3) is formed by a cavity in a plastic housing (2).
 3. The optoelectronic device of claim 1 or 2, characterized in that the partition (11) is formed by a reflective dividing rib, which in particular has a wedge-shaped cross section.
 4. The optoelectronic device of one of claims 1-3, characterized in that the light emitting diode chips (5) are arranged on a leadframe (6), which extends along the bottom of the reflector (3) or cavity.
 5. The optoelectronic device of one of claims 1-3, characterized in that the light emitting diode chips (5) are secured to conductor tracks (12), which are formed on the reflector (3) or in the cavity on the housing (2).
 6. The optoelectronic device of one of claims 1-5, characterized in that the reflector (3) is cast with a synthetic resin that is transparent to the radiation of the light emitting diode chips (5).
 7. The optoelectronic device of one of claims 1-6, characterized in that at least three light emitting diode chips (5) are arranged in the reflector (3) in such a way that they are arranged at the corner points of an imaginary polygon, and partitions (11) extend in starlike fashion apart from one another between the light emitting diode chips (5).
 8. The optoelectronic device of one of claims 1-7, characterized in that every two light emitting diode chips (5) have a spacing from one another of between 0.5 mm and 1 mm, and in particular of approximately 0.8 mm, in each case measured from the respective center of each light emitting diode chip (5).
 9. The optoelectronic device of one of claims 1-8, characterized in that the height of the partition (11) is up to 25% and in particular up to 10% above the height of the light emitting diode chips (5).
 10. The optoelectronic device of claim 2 or one of claims 3-9 with dependency from claim 2, characterized in that the partition (11) is formed onto the plastic housing (2) between each two light emitting diode chips (5). 